passing nil to split is not necessary

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30297 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/net/smtp.rb

@@ -1004,7 +1004,7 @@ module Net
         return {} unless @string[3, 1] == '-'
         h = {}
         @string.lines.drop(1).each do |line|
-          k, *v = line[4..-1].chomp.split(nil)
+          k, *v = line[4..-1].chomp.split
           h[k] = v
         end
         h